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Re: Performance on new 64bit server compared to my 32bit desktop

From: Greg Smith <greg(at)2ndquadrant(dot)com>
To: Scott Carey <scott(at)richrelevance(dot)com>
Cc: Philippe Rimbault <primbault(at)edd(dot)fr>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Performance on new 64bit server compared to my 32bit desktop
Date: 2010-08-27 17:25:08
Message-ID: 4C77F4F4.4020900@2ndquadrant.com (view raw or flat)
Thread:
Lists: pgsql-performance
Scott Carey wrote:
> But the select count(*) query, cached in RAM is 3x faster in one system than the other.  The CPUs aren't 3x different performance wise.  Something else may be wrong here.
>
> An individual Core2 Duo 2.93Ghz should be at most 50% faster than a 2.2Ghz Opteron for such a query.   Unless there are some compile options that are set wrong.   I would check the compile options.
>   

Sure, it might be.  But I've seen RAM on an Intel chip like the E7500 
here (DDR3-1066 or better, around 10GB/s possible) run almost 3X as fast 
as what you'll find paired with an Opteron 2427 (DDR2-800, closer to 
3.5GB/s).  Throw in the clock differences and there you go.

I've been wandering around for years warning that the older Opterons on 
DDR2 running a single PostgreSQL process are dog slow compared to the 
same thing on Intel.  So that alone might actually be enough to account 
for the difference.  Ultimately the multi-processor stuff is what's more 
important to most apps, though, which is why I was hinting to properly 
run that instead.

-- 
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg(at)2ndQuadrant(dot)com   www.2ndQuadrant.us


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Subject: Re: turn off caching for performance test
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